May 1st, 2017 – I picked up all the supplies to start the subfloor today. I’ll be using Dow Styrofoam XPS (Extruded Polystyrene) insulation. It comes in 4×8 ft. sheets and I’m using 1/2 inch thickness. The XPS is much denser and sturdier than the poly-iso type of foam board and holds up much better for using it on the floor. On top of that I’ll be using 1/2 inch plywood to help disperse the weight of cabinets, appliances, and us walking on it. Then on top of the plywood we’ll be putting Pergo laminate flooring.
The width inside the bus is exactly 7 ft. 6 in. I’m cutting the insulation at exactly 7 ft. 5 1/2 in. This leaves me with 1/4 inch on each end for expansion and contraction. I’m cutting the plywood at 7 ft. 4 1/2 in. so that it will clear the seat ledge. This will give me a 3/4 in. gap on each end of the plywood which I will cover up with 2×2’s at the bottom. I’ll speak more about this and include photos in my next post. I’m not putting down any framing to hold the insulation and plywood in place. Lots of people do that but it’s completely unnecessary. If you cut the insulation and plywood so that it only has a slight gap on each end then it’s not going to move and shift around. This way is called a “floating floor”. And once I attach the floor cabinets to the plywood and also to the side wall studs then the floor really won’t be floating anymore anyway. So once again the framing is not needed.
Some people lay the insulation horizontally and then the plywood vertically so that there are no matching seams between the pieces. That is not a bad way to do it but I chose to lay all of mine horizontally but to have the plywood overlap the insulation seams. This solved itself because of the 3 ft. storage/electrical room that I’m putting at the very back of the bus where only the insulation was laid down, and then the rubber mat. The rubber flooring was a steal at Costco for only $9.99.